The present invention generally pertains to fasteners and more particularly to a hybrid fastener having an insert between the fastener and a workpiece being joined.
It is known to use a fastener to secure a plurality of workpieces. It is also known to employ a ferrule around a shank of the fastener or an adhesive material to the threads of a fastener to strengthen the joint and/or to further secure the fastener to the workpieces. Examples of such traditional devices are disclosed in U.S. Pat. No. 3,472,301 entitled “Self-Sealing Mechanical Fastener;” U.S. Pat. Nos. 4,094,222 and 4,263,832 both entitled “Adhesively Secured Anchor Bolt;” U.S. Pat. Nos. 4,776,738 and 4,990,041 both entitled “Fastening Device;” and U.S. Pat. No. 5,249,899 entitled “Head Bolt and Driver Therefor;” all of which are incorporated by reference herein. Prior disclosed ferrules require precision machining and/or a large inventory of products to accommodate different fastener sizing, while prior adhesive materials are merely thin coatings along the threads of a fastener that provide no additional structure, cannot guarantee a filled gap, and have little to no stress-reducing properties. Furthermore, either design requires workpieces that are carefully machined, matched, and aligned.
In accordance with the present invention, an apparatus is provided having a fastener and a structural insert. In another aspect, the fastener includes a head and a shank. A further aspect provides at least one thread helically located about a shank. In still another aspect, an insert is disposed about a shank at an unthreaded section and extends at least partially into a head and/or the shank. In another aspect, a sleeve surrounds a shank of the fastener and has apertures extending therethrough. Yet another aspect provides a magnetically, electrically, or chemically attractive coating on the shank for attracting friable or elastomeric particles in a structural insert. In another aspect, electrically conductive particles are contained in the insert to accelerate curing by application of an electric field. In another aspect, the fastener is a self-drilling and self-tapping fastener. In another aspect, the fastener is a rivet. Methods of using the above-described hybrid fastener for securing workpieces are also disclosed.
The present hybrid fastener is advantageous over prior fastening members. For example, the present apparatus and method advantageously alleviate stress concentrations and contact stresses in workpieces being joined. Notably, the present hybrid fastener also works to seal edges of the apertures in the workpieces so as to preclude invasion by moisture or dirt. Moreover, the present apparatus effectively reduces costs by allowing increased tolerances for the workpiece apertures. Additional advantages and features of the present invention will be found in the following description and accompanying claims, as well as in the appended drawings.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.